diff --git a/gurubu-client/src/app/components/room/retro-board/RetroColumn.tsx b/gurubu-client/src/app/components/room/retro-board/RetroColumn.tsx
index 297f225..8c172f9 100644
--- a/gurubu-client/src/app/components/room/retro-board/RetroColumn.tsx
+++ b/gurubu-client/src/app/components/room/retro-board/RetroColumn.tsx
@@ -356,6 +356,7 @@ const RetroColumn = ({
             <input
               type="file"
               accept="image/*"
+              multiple={false}
               onChange={(e) => onColumnHeaderImageUpload(columnKey, e)}
               style={{ display: "none" }}
             />
diff --git a/gurubu-client/src/app/components/room/retro-board/RetroErrorPopup.tsx b/gurubu-client/src/app/components/room/retro-board/RetroErrorPopup.tsx
index 2b226ad..d6051d7 100644
--- a/gurubu-client/src/app/components/room/retro-board/RetroErrorPopup.tsx
+++ b/gurubu-client/src/app/components/room/retro-board/RetroErrorPopup.tsx
@@ -21,6 +21,9 @@ const RetroErrorPopup = ({ title, retroId }: IProps) => {
     const lobby = getCurrentRetroLobby(retroId);
 
     if (retroNickname && lobby) {
+      if (!socket.connected) {
+        socket.connect();
+      }
       socket.emit("joinRetro", {
         nickname: retroNickname,
         retroId: retroId,
diff --git a/gurubu-client/src/app/components/room/retro-board/hooks/useBoardImages.ts b/gurubu-client/src/app/components/room/retro-board/hooks/useBoardImages.ts
index b53679a..79cf09d 100644
--- a/gurubu-client/src/app/components/room/retro-board/hooks/useBoardImages.ts
+++ b/gurubu-client/src/app/components/room/retro-board/hooks/useBoardImages.ts
@@ -1,6 +1,10 @@
 "use client";
 
 import { useState, useEffect } from "react";
+import toast from "react-hot-toast";
+
+const MAX_HEADER_IMAGE_SIZE_BYTES = 1024 * 1024; // 1MB
+const MAX_HEADER_IMAGE_DIMENSION = 1200;
 
 interface UseBoardImagesParams {
   socket: any;
@@ -152,36 +156,54 @@ export const useBoardImages = ({
     const file = e.target.files?.[0];
     if (!file) return;
 
-    const reader = new FileReader();
-    reader.onload = (event) => {
-      const result = event.target?.result as string;
-      const img = new Image();
-      img.onload = () => {
-        const maxSize = 300;
-        let width = img.naturalWidth;
-        let height = img.naturalHeight;
-        if (width > maxSize || height > maxSize) {
-          const ratio = Math.min(maxSize / width, maxSize / height);
-          width = width * ratio;
-          height = height * ratio;
-        }
-        const newImage = {
-          id: Date.now().toString(),
-          src: result,
-          x: -99999,
-          y: -99999,
-          width,
-          height
-        };
-        const updatedImages = [...boardImages, newImage];
-        setBoardImages(updatedImages);
-        if (userInfo.lobby) {
-          socket.emit("updateBoardImages", roomId, updatedImages, userInfo.lobby.credentials);
+    try {
+      const reader = new FileReader();
+      reader.onload = (event) => {
+        try {
+          const result = event.target?.result as string;
+          const img = new Image();
+          img.onload = () => {
+            try {
+              const maxSize = 300;
+              let width = img.naturalWidth;
+              let height = img.naturalHeight;
+              if (width > maxSize || height > maxSize) {
+                const ratio = Math.min(maxSize / width, maxSize / height);
+                width = width * ratio;
+                height = height * ratio;
+              }
+              const newImage = {
+                id: Date.now().toString(),
+                src: result,
+                x: -99999,
+                y: -99999,
+                width,
+                height
+              };
+              const updatedImages = [...boardImages, newImage];
+              setBoardImages(updatedImages);
+              if (userInfo.lobby) {
+                socket.emit("updateBoardImages", roomId, updatedImages, userInfo.lobby.credentials);
+              }
+            } catch (err) {
+              console.error("Board image process error:", err);
+              toast.error("Failed to process image");
+            }
+          };
+          img.onerror = () => toast.error("Invalid image file");
+          img.src = result;
+        } catch (err) {
+          console.error("Board image load error:", err);
+          toast.error("Failed to load image");
         }
       };
-      img.src = result;
-    };
-    reader.readAsDataURL(file);
+      reader.onerror = () => toast.error("Failed to read file");
+      reader.readAsDataURL(file);
+    } catch (err) {
+      console.error("Board image upload error:", err);
+      toast.error("Failed to upload image");
+    }
+    e.target.value = "";
   };
 
   const handleImageDragStart = (image: any, e: React.DragEvent) => {
@@ -213,16 +235,77 @@ export const useBoardImages = ({
   const handleColumnHeaderImageUpload = (columnKey: string, e: React.ChangeEvent<HTMLInputElement>) => {
     const file = e.target.files?.[0];
     if (!file) return;
-    const reader = new FileReader();
-    reader.onload = (event) => {
-      const result = event.target?.result as string;
-      const updatedImages = { ...columnHeaderImages, [columnKey]: result };
-      setColumnHeaderImages(updatedImages);
-      if (userInfo.lobby) {
-        socket.emit("updateColumnHeaderImages", roomId, updatedImages, userInfo.lobby.credentials);
-      }
-    };
-    reader.readAsDataURL(file);
+
+    // Tek image: zaten varsa yükleme (UI'da gizli ama yine de guard)
+    if (columnHeaderImages[columnKey]) {
+      toast.error("Only one image per column. Remove the current image first.");
+      return;
+    }
+
+    if (file.size > MAX_HEADER_IMAGE_SIZE_BYTES) {
+      toast.error("Image must be under 1MB");
+      return;
+    }
+
+    try {
+      const reader = new FileReader();
+      reader.onload = (event) => {
+        try {
+          const result = event.target?.result as string;
+          const img = new Image();
+          img.onload = () => {
+            try {
+              let width = img.naturalWidth;
+              let height = img.naturalHeight;
+              if (width > MAX_HEADER_IMAGE_DIMENSION || height > MAX_HEADER_IMAGE_DIMENSION) {
+                const ratio = Math.min(MAX_HEADER_IMAGE_DIMENSION / width, MAX_HEADER_IMAGE_DIMENSION / height);
+                width = Math.round(width * ratio);
+                height = Math.round(height * ratio);
+                const canvas = document.createElement("canvas");
+                canvas.width = width;
+                canvas.height = height;
+                const ctx = canvas.getContext("2d");
+                if (ctx) {
+                  ctx.drawImage(img, 0, 0, width, height);
+                  const resizedBase64 = canvas.toDataURL("image/jpeg", 0.85);
+                  const updatedImages = { ...columnHeaderImages, [columnKey]: resizedBase64 };
+                  setColumnHeaderImages(updatedImages);
+                  if (userInfo.lobby) {
+                    socket.emit("updateColumnHeaderImages", roomId, updatedImages, userInfo.lobby.credentials);
+                  }
+                } else {
+                  const updatedImages = { ...columnHeaderImages, [columnKey]: result };
+                  setColumnHeaderImages(updatedImages);
+                  if (userInfo.lobby) {
+                    socket.emit("updateColumnHeaderImages", roomId, updatedImages, userInfo.lobby.credentials);
+                  }
+                }
+              } else {
+                const updatedImages = { ...columnHeaderImages, [columnKey]: result };
+                setColumnHeaderImages(updatedImages);
+                if (userInfo.lobby) {
+                  socket.emit("updateColumnHeaderImages", roomId, updatedImages, userInfo.lobby.credentials);
+                }
+              }
+            } catch (err) {
+              console.error("Header image process error:", err);
+              toast.error("Failed to process image");
+            }
+          };
+          img.onerror = () => toast.error("Invalid image file");
+          img.src = result;
+        } catch (err) {
+          console.error("Header image load error:", err);
+          toast.error("Failed to load image");
+        }
+      };
+      reader.onerror = () => toast.error("Failed to read file");
+      reader.readAsDataURL(file);
+    } catch (err) {
+      console.error("Header image upload error:", err);
+      toast.error("Failed to upload image");
+    }
+    e.target.value = "";
   };
 
   const handleRemoveColumnHeaderImage = (columnKey: string) => {
diff --git a/gurubu-client/src/app/components/room/retro-board/hooks/useRetroSocketEvents.ts b/gurubu-client/src/app/components/room/retro-board/hooks/useRetroSocketEvents.ts
index 5e47561..e2ed10d 100644
--- a/gurubu-client/src/app/components/room/retro-board/hooks/useRetroSocketEvents.ts
+++ b/gurubu-client/src/app/components/room/retro-board/hooks/useRetroSocketEvents.ts
@@ -206,6 +206,11 @@ export const useRetroSocketEvents = ({
     socket.on("emoteReaction", handleEmoteReaction);
     socket.on("retroEnded", handleRetroEnded);
 
+    const handleDisconnect = () => {
+      setShowErrorPopup(true);
+    };
+    socket.on("disconnect", handleDisconnect);
+
     return () => {
       clearInterval(heartbeatInterval);
       document.removeEventListener('visibilitychange', handleVisibilityChange);
@@ -235,6 +240,7 @@ export const useRetroSocketEvents = ({
       socket.off("cardsImported", handleCardsImported);
       socket.off("emoteReaction", handleEmoteReaction);
       socket.off("retroEnded", handleRetroEnded);
+      socket.off("disconnect", handleDisconnect);
     };
   }, [socket, roomId, avatarSeed]);
 };
diff --git a/gurubu-client/src/app/styles/room/retro-board/retro-board.scss b/gurubu-client/src/app/styles/room/retro-board/retro-board.scss
index 75a7ce9..4884c8b 100644
--- a/gurubu-client/src/app/styles/room/retro-board/retro-board.scss
+++ b/gurubu-client/src/app/styles/room/retro-board/retro-board.scss
@@ -2149,7 +2149,7 @@
   &__header-image {
     position: relative;
     width: 100%;
-    height: 120px;
+    height: 200px;
     margin-bottom: 1rem;
     overflow: hidden;
     border-radius: 8px;